In mass transfer processes such as waste treatment and bio-reactions, it is common to carry out these processes in an aeration vessel in which gas, such as oxygen and/or air, is introduced into a biodegradable liquid for treatment. These aforementioned processes are oftentimes utilized by municipalities and industry to treat waste water wherein the object of the process is to introduce air to the liquid and then micro-organisms in the liquid proceed to use this oxygen to digest the waste. The gas and/or air is commonly introduced by way of impellers, wherein the impellers aerate the liquid.
In aeration processes such as waste water treatment, it is common to employ impellers which are especially adapted for use on the surface of liquids in an open tank called surface aerators. Typical surface aerators commonly used in the art are generally either radial flow impellers or pitched blade turbines and/or disc impellers. The blades are usually flat, rectangular plates, which are pitched usually at an angle of 45° to the axis of rotation of the impeller. The aforementioned impellers are commonly located close to the static level liquid surface and a small portion of the width of the blade may project up through the surface. Typically, when the impeller is pitched forwardly, the upper edge of the blade is the leading edge while lower edge is the trailing edge. Alternatively, when the impeller is pitched backwardly, the upper edge is the trailing edge while the lower edge is the leading edge. The liquid is usually either pushed out in front of the angled blade and/or scooped by the blade and discharged radially across the surface of the tank with some of the liquid being sprayed into the atmospheric air from the outer upper surfaces of the blade. As a result of the spraying of the liquid into the atmospheric air, the liquid becomes aerated.
One disadvantage of the above described processes and impellers is that they can be very inefficient. The length of time required to effect the oxidation treatment can be as long as 24 hours. This time period combined with the fact that these waste treatment processes are oftentimes carried out continuously year round, provide a process that is very inefficient in terms of both time consumption and energy consumption.
Accordingly, it is desirable to provide an aeration apparatus and method for effectuating the more efficient dispersement or transfer of air and/or other gases into a liquid.